Holder for grinding threading tools and the like



Nov. 17, 1959 E. w. SHERMAN 2,912,801

HOLDER FOR GRINDING THREADING .-.TOOLS AND THE L1IKE Filed July 5. 1957 5 She'e ts-Sheet 1 INVENTOR.

BY Ju /1v WW-$68 744 Nov. 17, 1959 E. w. SHVERMAN 2,

HOLDER FOR GRINDING THREADING TOOLS AND LIKE FilOd July 5, 1951 5 Sheets-Sheet 2 INVENTOR. f o'W/k WSfi M n rro ZNE) Nov. 17, 1959 E. w. SHERMAN 2,912,801 HOLDER FOR GRINDING THREADING TOOLS AND THE LIKE Filed-July 5. 1957 5 Sheets-Sheet 3 Nov. 17, 1959 E. w. SHERMAN 2,912,801

HOLDER FOR GRINDING THREADING TOOLS AND THE LIKE F1106 July 5, 1957 5 Sheets-Sheet 4 v INVENTOR.

BY Ed /5v WSWerM United States Patent HOLDER FoR GRINDING THREADING TOOLS AND THE LIKE Edwin W. Sherman, Detroit, Mich.

Application July 5, 1957, Serial No. 670,180

9 Claims. (Cl. 51-220) This invention relates to a fixture for grinding thread cutting tools and more particularly to a holder block adapted for mounting upon the bed of a surface grinder for the purpose of supporting and securing a thread cutting tool'with respect to the grinding wheel thereof.

It is the object of the present invention to provide a simple fixture or block construction to provide for the accurate grinding of Acme and US. Standard threading tool bits, offset to the right or to the left without the aid of a sine plate, angle block, shim or other removable parts.

It is the further object herein to provide a fixture block for holding thread cutting tools for grinding the respec tive surfaces thereof and wherein it is unnecessary to move the tool bit with respect to the supporting block until all cutting angles have been ground, thus assuring greater accuracy.

It is another object of the present invention to provide the fixture in the nature of a unitary block slotted adjacentone surface to receive and support a thread cutting tool, secured therein to facilitate grinding of its surfaces and wherein there are no moving parts or adjustments,

"once the particular set screw or set screws have been tightened.

' It is the further object to provide a novel fixture or holder for the grinding of thread cutting tools which consists of a unitary block having a series of angularly related flat surfaces at predetermined angles with respect to the longitudinal axis of the tool receiving slot whereby the mounting of a particular angular block surface upon the bed of a surface grinder will present a corresponding surface to the grinding wheel for achieving in said tool a cutting surface at a corresponding angle to its longitudinal axis.

It is a further object of the present invention to provide a simple and accurate method of grinding tool bits i.e., ID. or O.D., for threading, grooving, boring, turning or in forming chip breakers, or other tools.

These and other objects will be seen from the following specification and claims in conjunction with the appended drawings in which:

Fig. 1 is a front elevational view of one form of fixture block arranged upon the bed of a grinder for the formation of a surface on the tool providing a side clearance angle.

Fig. 2 is a similar view showing the block rotated clockwise and positioned upon one angular surface for the grinding of a corresponding angular surface on one end of the'tool bit for the formation of U.S. Standard threads.

Fig. 3 is a similar view with the block rotated counterclockwise from Fig. 1 and mounted upon an opposing angular surface for the formation of a corresponding angular surface at the opposite end of the tool or of a second tool secured within said block.

Fig.4 is a perspective view of the block as viewed from the rear side of Fig. 1.

Fig. 5 is a front elevational view of a slightly different form of fixture block with its angular bottom surface posi- 2,912,801 Patented Nov. 17, 1959 tioned upon the bed of a grinder for the formation of corresponding side clearance angles at the cutting ends of a pair of tools.

Fig. 6 is a similar view with the block rotated counterclockwise for support upon one of its angular end surfaces to permit the grinding of a corresponding tapered side on the tool for the formation of Acme threads.

Fig. 7 is a similar view showing said block rotated clockwise and supported on a second angular end surface for the grinding of a corresponding angular cutting edge upon a tool bit for cutting Acme threads.

Fig. 8 is a similar view but with the fixture block rotated for support upon a different angular surface for the grinding of a transverse front surface at the end of the tool for the formation of the thread roots for Acme threads.

Fig. 9 is a similar view with the fixture block supported upon a second but corresponding angular surface for the grinding of the end face of a second Acme thread tool.

Fig. 10 is a side elevational view of another form of slotted tool receiving fixture block having a series of angularly related plane surfaces adapted for mounting upon the table of a surface grinder for the grinding of angularly related surfaces upon the heads of an internal diameter Acme thread cutting tool.

Fig. 11 is a similar view showing the fixture block mounted upon another of these surfaces for the grinding of the angularly related cutting edges of a US. Standard I.D. thread cutting tool.

Fig. 12 is a side elevational View of this same fixture block when supported upon one of its other angularly related surfaces for the grinding of side clearance angles on the heads of a grooving tool.

Fig. 13 is a similar view of the fixture block for the cutting of a side clearance angle on another form of cutting tool.

Fig. 14 is a similar view but with the block mounted upon its opposite angular surface upon the bed of a surface grinder for cutting the clearance angle on the opposite side of said tool head.

Fig. 15 is a view similar to Fig. 10 for the purpose of grinding an angular surface upon a chip breaker.

Fig. 16 is an end elevational view of the fixture block support in upright position supported upon an angularly related end surface for forming an end clearance angle for the tool.

Figs. 17, 19, 21, 23, 25, 27, 29, 31 and 33 illustrate different types of cutting tools or the like, which may be formed using the above described fixture blocks and which are identified respectively as plane Acme, US. Standard, US. Standard I.D., Acme I.D., chip breaker, grooving tool, I.D. grooving tool, I.D. Acme tool bit on boring bar, and US Standard I.D. tool bit on boring bar.

Figs. 18, 20, 22, 24, 26, 28, 30, 32 and 34 are respectively end elevational views of the tools shown in Figs. 17,19, 21, 23, 25, 27, 29, 31 and 33.

It will be understood that the above drawings illustrate several preferred embodiments of the present fixture block for the grinding of thread cutting and other tools, and that other embodiments are contemplated within the scope of the claims hereafter set forth.

Referring to the drawings, Figs. 1 through 4 illustrate one form of fixture block 11 as mounted upon the top surface of the table or bed T of a conventional surface grinder.

For the purpose of this disclosure, it is contemplated that a magnetic type of table is employed and with the respective fixture blocks hereafter described and shown of a magnetizable material, such as steel, whereby the block will immovably adhere to the surface of table T for positioning with respect to the grinding surface of the abrasive grinding wheel W fragmentarily shown in phantom lines in each of the several views herein. These blocks could be immovably secured by suitable clamps if desired.

Block 11 has a fiat rear reference surface 12 which has formed therein the undercut horizontally elongated slot 13 of rectangular cross section defined by the parallel side walls 14 and 15 which are normal to surface 12 and the bottom surface 16 which is parallel thereto. Slot 13 is adapted to cooperatively receive the elongated cutting tool C shown in Figs. 1, 2, 3 which may be a unit or a pair of such tools.

It is contemplated that these tools will be of different dimensions and accordingly though Fig. 1 shows a tool snugly received within slot 13 in more cases than not, the tool will be undersize with respect thereto.

For the purpose of immovable securing the tool C within said slot, there is provided the transverse threaded aperture 27 which extends normally inward from the top wall 19 of said block, and which wall is arranged at right angles to rear wall 12. Aperture 27 receives set screw 18 which extends parallel to surface 12 for operatively and retainingly engaging tool bit C within slot 13.

From the bottom surface 20, which is arranged at an acute angle with respect to top surface 19, there are a. pair of transverse threaded apertures 27, Fig. 4 for re-- ceiving additional set screws 28 for the securing of a pair of tool bits within slot 13.

Additional threaded apertures 29 project normally inward from slotted rear wall 12 and are adapted to receive suitable fasteners for an arbor or other securing means in the event that a tool bit of irregular cross section or a tool bit of circular cross section is positioned within slot 13.

The bottom surface 29 in the preferred embodiment is arranged at an angle of approximately degrees out of parallel to top surface 19 and accordingly at a similar angle with respect to the longitudinal axis of slot 13 and tool C secured within the block. Accordingly the wheel W fragmentarily shown, will grind a side clearance angular surface 21 at the opposite ends of the tool or tools, which will be at a corresponding angle with respect to the tool axis.

Block 11 has a front surface 22 which is parallel to the slotted rear surface 12. The opposite ends of said block are defined by a pair of flat rearwardly and outwardly diverging angular surfaces A and B which ex tend respectively at a 60 degree angle with respect to the tool slot axis, and in respect to each other.

As shown in Fig. 2 the block of Fig. 1 has been rotated clockwise so that its end surface B rests upon table T. In this position wheel W will grind a flat surface 23 at one end of the tool C which extends at a 60 degree angle with respect to the tool axis. This surface cooperates with the straight side edge 24 of the tool which is parallel to the tool axis, and thereby provides a pair of side cutting edges arranged at an angle of 60 degrees for the formation of US. StandardV-threads, said converging edges terminating in the sharpened front edge 2:3.

In the present preferred embodiment, the side cutting edges of the thread cutting tool C are defined by a pair of surfaces one of which, such as surface 24, is parallel to a tool axis. Accordingly, it is necessary to grind one side of the tool bit as at the surface 23, Fig. 2, to define its cutting end.

Fig. 3 illustrates the use of the present block when supported upon its other 60 degree angular surface A for cutting the tapered side surface 23 at the corresponding opposite end of the tool C. This surface and surface 24- define the cutting edge for a US. Standard V-thread to be cut by said tool.

The clearance surfaces 2d shown in Figs. 2 and 3 are arranged at 29 degrees with respect to the opposite edge 24 of the tool and provide clearance which is useful in the cutting of threads to a shoulder of a workpiece. Such surface 26 would be cut using the block shown in Fig. 6.

Accordingly as these end surfaces A and B are supported upon table T the respective surfaces 23 ground in the tools will be arranged at an angle of 60 degrees with respect to the tool axes even though cut in a horizontal plane, producing a tool similar to that shown in Figs. 19 and 20.

Figs. 5 through 9 show a slightly different form of fixture block for the grinding of an Acme thread cutting tool. The unitary block 349 has a flat front face 31 and cut thereinto the horizontally disposed tool receiving slot defined by parallel side walls 32 normal to surface 31 and the bottom wall 32' parallel to surface 31.

Fig. 5 shows a pair of oppositely arranged separate tools C arranged within the tool slot and secured therein by set screws 3'5 which are adjustably positioned within upright threaded apertures 34- which extend from the bottom surface 36 of the block and are substantially normal to the said tools and parallel to surface 31. Slot 3232' is rectangular in cross section. Tool C may be undersized with respect to said slot.

An oppositely arranged threaded opening 34 is formed in said block extending from the top thereof adapted to receive the additional set screw 33 in the event that a unitary tool is positioned within the slot.

The bottom surface 36 of said block is tapered with respect to a plane normal to front surface 31 approximately 12 degrees to thereby provide a corresponding inclination with respect to the tool slot.

Accordingly grinding wheel W forms a side clearance surface 37 in the tools C which is arranged at an angle of approximately 12 degrees corresponding to the inclination of bottom surface 36 with respect to the longitudinal axis of tool slot 32 and 32'.

The top portion of block 30 has formed thereon a pair of perfectly flat angularly related surfaces C and D' each of which is formed at an angle of 29 degrees with respect to the longiutdinal axis of the tool slot. Accordingly when the block 30 is rotated less than degrees counterclockwise to the position shown in Fig. 6, the properly positioned wheel W will grind the angular surface 38 at a corresponding 29 degree angle with respect to the tool axis and with respect to its opposite straight side 39. This second machining of tool C is done without changing the related position of tool and block.

When the corresponding side edges of the tool are arranged at a 29 degree angle for the purpose of providing a tool which will cut Acme threads, it is important to note that only one of the side edges of the tool is cut angularly. This is an advantage of reducing the time in forming the cutting edge and in regrinding the same from time to time. Furthermore, it follows that a higher degree of accuracy is maintained where only one of the side edges is ground.

Fig. 7 illustrates the block of Fig. 5 as rotated clockwise less than 180 degrees so as to rest upon its other 29 degree angular surface D. Accordingly wheel W will grind the 29 degree angular side edge 38 in the tool C with respect to the tool axis and with respect to the straight side 39, parallel to the tool axes.

Additional threaded apertures 41 are formed normally of front wall 31 of the block to facilitate the securing thereto of a suitable arbor or other clamp for retaining engagement with a tool of irregular cross sectional shape or of circular cross section.

As ground, Figs. 6 and 7, the end edge of the Acme thread tool is sharp as at 40. As the Acme thread has a root between each thread, the sharp end it? shown in Figs. 6 and 7 must be transversely ground at the correct angle to produce the front edge face 42 shown in Figs. 8 and 9. This is for the purpose of cutting the required root between threads.

Block 30 has a pair of perfectly flat angularly related end surfaces E and F respectively which are arranged at an angle of approximately 14 /2 degrees off the normal with respect to the tool slot axis.

This means that with the block 30 rotated so as to be supported on either of the surfaces E or F in Figs. 8 and 9 respectively, the wheel W will cut in the end of the tool the tapered front face 42. This edge is 14 /2 degrees off the normal with respect to each of the angularly related surfaces 38 and 39 which define the cutting edge of the Acme thread cutting tool C.

A slightly different form of fixture block 43 is shown in Figs. through 16. This block is of a unitary construction and has a top fiat surface 44, Fig. 10; and there is formed by broaching or otherwise a tool receiving slot defined by the bottom wall 45 parallel to top surface 44 and the spaced sidewalls 46 at right angles to surface 44.

This slot, rectangular in cross section, accordingly has an axis parallel to reference surface 44 and is adapted to receive tool 47 whose respective transversely arranged heads 48 at opposite ends are to be formed for the cutting of ID. threads.

The upright front wall G approximately normal to top surface 44 has formed transversely thereof a series of threaded apertures 49 to receive set screws 50 for operative engagement with central portions of tool 47.

The opposing wall H, Fig. 12, arranged at approximately a 2 degree angle with respect to Wall G also has formed transversely thereof a similar series of opposed threaded apertures 49 to receive additional set screws 50, for securing cutting tool 47 from its opposite side if desired.

The bottom surface 51 of block 43 is perfectly flat and is arranged preferably at an angle of 14 /2 degrees with respect to the axis of the tool slot. Accordingly when the tool 47 is properly positioned and secured within block 43 upon table T wheel W will grind the upright surface 52 which will be at an angle 29 degrees with respect to the opposing surface 55 in the cutting head 48 when ground, i.e., at 14 /2 degrees to a normal of the tool axis.

The grinding wheel shown at the left end of Fig. 10 grinds an upright inner surface 52, whereas at the opposite end of tool 47 forms the upright outer surface 53 likewise at a 14 /2 degree angle to said normal. Thereafter by reversing the tool endwise with respect to the tool slot and repeating grinding operations, the tool will be so presented. that the said wheel W will grind the additional surfaces 54-55 respectively which, of course, will be arranged at a 29 degree angle with respect to the corresponding tapered surfaces 53 and 52 respectively.

Accordingly the respective heads 48 of cutting tool 47 have properly tapered cutting side edges which will form Acme threads for ID. threading, except that the sharpened end edges must be flattened to form thread roots.

Block 43 has a second perfectly flat angular surface 56 which is arranged at approximately a 30-degree angle to the axis of the tool receiving slot. Accordingly, when block 43 is supported upon surface 56 upon table T as in Fig. 11, wheel W will form the upright side surfaces 59 and 60, which will be arranged at 60 degrees with respect to the subsequently formed side cutting surfaces 62 and 61. For this purpose the tool 57 is changed end for end within the tool slot so that the respective heads 58 will be presented to grinding wheel W to permit grinding of surfaces 61 and 62 which in cooperation with surfaces 60 and 59 form the 60 degree related cutting ends for the cutting of U.S. Standard I.D. V-threads.

Fig. 12 illustrates the use of block 43 when supported upon one of its side surfaces G. Surface G is tapered for example at a one degree angle with respect to the tool slot axis. Similarly, the opposing surface H is tapered at a one degree angle with respect to the tool slot axis. Thus surfaces G and H are arranged at an angle of Z-degrees with respect to each other,

Fig. 12 illustrates theuse. ofblock 43 when supported upon its; surface G upon table T, fragmentarily shown, forming part of a suitable grinder for the forming of tapered clearance edges of an ID. grooving tool.

As shown. in Fig. 12 the tools C are suitably secured Withinthe. tool slot adjacent face 44 by a series of set screws 50. In View of the one degree angle of surface G with. respect to the tool slot axis, in the position shown, wheel W grinds the surfaces 6364 at the outer ends of the respective tools. These surfaces are tapered at a corresponding; one-degree angle off the normal with respect tothe tool axes.

By rotating block 43 degrees on table T it is seen that wheel W will grind the additional surfaces 65 and 66 which are likewise tapered at a one-degree angle with respect to the normal to the tool axis.

In other words, the respective cutting edges 63 and 65 as well as cutting edges 64 and 66 will be inclined betweeneachother in one direction at an angle of 2-degrees which corresponds to the inclination of block surfaces G and H with respect to each other.

Fig. 13 shows this second position of block 43 as sup ported upon'its surface G. In Fig. 13 a different form of cutting tool C is positioned within the slot 4546 adjacent end face. 44 to permit the one degree clearance surface70 tobe ground'adjacent the cutting edge of said tool.

Fig. 14 shows the same block resting upon surface H for the formation of the one degree tapered or clearance surface69. Rotationof each of the blocks 43l80 de grees from the respective positions shown in Figs. 13 and 14, will provide for the additional cutting of the one degree tapered surfaces 69 and 70, left uncut in Figs. 13 and 1.4.

For the purpose of forming a. tapered front face of tool C, the block 43. is rotated Fig. 16 so that its surface I is positionedat table T, fragmentarily shown forming a part of a conventional surface grinder. Surface I is inclined at an angle of approximately 10 degrees with respect to plane normal to the tool slot axis with the result that wheeLW grinds a similarly tapered end face '72.

The block 43, shown in Fig. 15 is returned to the position shown in Fig. l0, and wherein it is supported upon surface 51 which is inclined at an angle of 14 /2 degrees with respect to the tool slot axis. It therefore follows that the upright grinding wheel W, fragmentarily shownin phantom, will grind a correspondingly inclined surface-71 in the end of the chip breaker C.

Figs. 17 and 18 illustrate an Acme thread cutting tool formed from the block 30 shown in Figs. 5 through 9 andwhich includes the clearance surfaces 37 and the cutting surfaces38 and39, one of which is parallel to the toolfaxis and the other arranged at a 29 degree angle to the toolaxis. and with the tapered front face 42 formed thereon inthe manner shown in Figs. 8 and 9.

Figs. 19 and 20 show a U.S. Standard thread cutting tool 17 such as shown in Fig. 1 which has a pair of angular 1y relatedcutting surfaces 23 and 24, one of which is arranged at a 60 degree angle to the tool axis and the other is parallel thereto'and which has the sharpened cutting end 25 for the formation of the U.S. Standard threads.

This tool also has the tapered clearance surface 26 formed therein, also shown in Fig. 2, and which is achieved by using block 30 in either of the positions shown in Figs. 5 and 6.

Figs. 21 and 22 illustrate a U.S. Standard I.D. thread cutting tool 57 including. the angularly related cutting surfaces 60 and 61, produced by using block 43 as in Fig. 11.

Figs. 23 and 24 illustrate an Acme I.D. threading tool with angularly related cutting surfaces 52 and 55 produced' by the fixture block shown in Fig. 10.

Figs. 25 and 26 illustrate a chip breaker 73, whereas Figs. 27"and 28 show an OD. grooving tool 74 and Figs. 29and' 30 the ID. grooving tool 75.

Figs. 31 and 32 show a boring bar 76 carrying an Acme I.D. tool bit whereas boring bar 77 in Figs. 33 and 34 carries a U.S. Standard I.D. tool bit formed in accordance with the present invention.

One important element of the present fixture blocks described herein resides in the fact that these blocks have a series of angularly related surfaces formed thereon adapted for mounting upon the flat surface of a surface grinder. These surfaces are arranged at predetermined angles with respect to a tool slot formed in one of the surfaces of the block for the purpose of grinding corresponding angular surfaces in tools secured within said fixture blocks.

The present fixture blocks incorporate no moving parts or adjusting features. Accordingly, it is unnecessary to remove the tool bit until all cutting angles are ground. This'assures greater accuracy in the grinding of the particular tool bit and in re-grinding.

Having described my invention, reference should now be had to the following claims.

I claim:

1. A fixture block for supporting a tool on the table of a grinder having a wheel, the block including a unitary body having a fiat upwardly inclined reference surface, with an undercut slot of rectangular cross section therein, laterally terminating in said surface and having a longitudinal axis parallel thereto defining an opening for receiving a tool with a portion of the tool projecting from one end of the body, set screws in the body to operatively and retainingly engage a tool in said slot, the body having a fiat bottom surface lying in a plane parallel to the longitudinal axes of the slot and the tool therein, and inclined transversely at an acute angle of approximately degrees to said reference surface, whereby with said bottom surface engaging said table, the wheel grinds a clearance surface on the upwardly facing side of the tool which lies in a plane inclined at a corresponding acute angle to the top surface of the tool, said body having a pair of flat obtuse angularly related upwardly and inwardly inclined top surfaces, each lying in a plane at a 29 degree angle to the longitudinal axes of said slot and tool, so that with one of said top surfaces selectively engaging said table the wheel grinds a cutting edge on the upwardly facing end of the tool from one side thereof inclined at a 29 degree angle to the tool axis and intersecting the opposing straight side of the tool, said body including a pair of upwardly and outwardly diverging 60 degree angularly related end surfaces, each inclined at an angle of 14 /2 degrees to a normal extending from the tool slot axis, so that with one of said end surfaces selectively positioned on said table, the wheel grinds a flattened and tapered thread root cutting front edge in the cutting end of the tool lying in a plane respectively at 14 /2 degrees to normals extending respectively from the straight side of the tool and the 29 degree angular side of the tool.

2. A fixture block for supporting a tool on the table of a grinder having a wheel, the block including a unitary body having a flat upwardly inclined reference surface with an undercut slot of rectangular cross section therein, laterally terminating in said reference surface and having a longitudinal axis parallel thereto defining an opening for receiving a tool with a portion of the tool projecting from one end of said body, set screws in the body to operatively and retainingly engage a tool in said slot, said body having a pair of fiat obtuse angularly related upwardly and inwardly inclined top surfaces, each lying in a plane at a 29 degree angle to the longitudinal axes of said slot and tool, so that with one of said top surfaces selectively engaging said table the wheel grinds a cutting edge on the upwardly facing end of the tool from one side thereof inclined at a 29 degree angle to the tool axis and intersecting the opposing straight side of the tool, said body including a pair of upwardly and outwardly diverging 60 degrees angularly related end surfaces, each inclined at an angle of 14 /2 degrees to a normal extending from the tool slot axis, so that with one of said end surfaces selectively positioned on said table, the wheel grinds a flattened and tapered thread root cutting front edge in the cutting end of the tool lying in a plane respectively at 14 /2 degrees to normals extending respectively from the straight side of the tool and the 29 degree angular side of the tool.

3. A fixture block for supporting a tool on the table of a grinder having a wheel, the block including a unitary body having a flat upwardly inclined top reference surface with an undercut slot of rectangular cross section therein opening upwardly and terminating in said reference surface and having a longitudinal axis parallel thereto defining an opening for receiving a tool with portions thereof projecting from opposite ends of said body, set screws in the body to operatively and retainingly engage a tool in said slot, the body having two flat adjoining angularly related bottom surfaces on its under side, one bottom surface lying in a plane at a 14 /2 degree angle to the longitudinal axes on said slot and tool, so that when said bottom surface engages said table the wheel successively grinds inner and outer I.D. thread cutting surfaces respectively on opposite end portions of said tool, each cutting surface inclined 14 /2 degrees to a normal extending fro-m the tool axis, the other bottom surface lying in a plane inclined at a 30 degree angle to the longitudinal axes of said slot and tool, so that when said other bottom surface engages said table the wheel will successively grind inner and outer I.D. thread cutting surfaces on opposite end portions of a tool in said slot, each cutting surface inclined 30 degrees to a normal extending from the tool axis.

4. The fixture block of claim 3 said body including an upright fiat side wall inclined at approximately a onedegree angle to the longitudinal axes of said slot and tool whereby with said side wall registering with said table the wheel grinds side clearance surfaces, one side of the ends of the tool inclined at a corresponding one-degree angle to a normal extending from said tool axis, rotation of said body degrees upon said side wall so presenting said tool ends that said wheel grinds opposing clearance surfaces on the other sides of the ends of the tool inclined in the opposite direction one-degree to a normal extending from said tool axis, said body including a flat end surface inclined at an acute angle to the longitudinal axes of said slot and tool whereby with said inclined surface resting upon said table the wheel grinds a correspondingly tapered end surface in the tool.

5. A fixture block for supporting a tool on the table of a grinder having a wheel, the block including a unitary body having a flat upwardly inclined top reference surface with an undercut slot of rectangular cross section therein opening upwardly and terminating in said reference surface and having a longitudinal axis parallel thereto defining an opening for receiving a tool with portions thereof projecting from opposite ends of said body, set screws in the body to operatively and retainingly engage a tool in said slot, the body having flat front and rear surfaces each inclined oppositely and at approximately a one-degree angle to the longitudinal axes of said slot and tool, whereby with said front and rear surfaces successively resting upon said table the wheel grinds in the tool opposing oppositively inclined side clearance surfaces, each at a corresponding angle to the tool axis.

6. A tool for cutting U.S. Standard threads comprising an elongated body of rectangular cross section with parallel spaced side walls and a top wall, there being a thread cutting head on one end of the body including a straight side edge parallel to the longitudinal axis of the body and to one side wall, and an opposing tapered side edge extending at a 60-degree angle throughout the height of said body from the opposite side wall to said straight edge defining therewith at their intersection a sharpened cutting edge, said straight side edge adjacent said head being tapered downwardly and inwardly at an angle less than 90 degrees with respect to the top wall of the body defining a clearance angle.

7. A tool for cutting U.S. Standard threads comprising an elongated body of rectangular cross section with parallel spaced side walls and a top wall, there being a thread cutting head on one end of the body including a straight side edge parallel to the longitudinal axis of the body and to one side Wall, and an opposing tapered edge extending at a 60-degree angle rearward from said straight edge throughout the body height and terminating in a rearwardly tapered clearance edge at an angle of approximately 29 degrees relative to the body axis and joining the other side wall.

8. A tool for cutting Acme threads comprising an elongated body of rectangular cross section with parallel spaced side walls and a top wall, therein being a thread cutting head on one end of the body including a straight side edge parallel to the longitudinal axis of the body and to one side wall, and an opposing tapered side edge extending at a 29-degree angle from the opposite side wall to said straight edge throughout the height of said body, there being a flattened downwardly and rearwardly tapered thread root cutting front edge face on said head interconnecting said straight side edge and said tapered side edge at 14 /2 degree angles to normals extending respectively therefrom, said straight side edge adjacent said head being tapered downwardly and inwardly at an angle less than 90 degrees with respect to the top Wall of the body defining a clearance angle.

9. A fixture block for supporting a tool on the table of a grinder having a wheel, the block including a unitary body having a flat upwardly inclined reference surface with an undercut slot of rectangular cross section therein, laterally terminating in said surface and having a longitudinal axis parallel thereto defining an opening for receiving a tool with a portion of the tool projecting from one end of the body, set screws in the body to operatively and retainingly engage a tool in said slot, the body including a pair of opposing rearwardly and laterally diverging fiat end surfaces, each inclined inwardly and upwardly at 60 degree angles to the longitudinal axes of said slot and tool, and lying in 6t) degree related planes, so that with one of said end surfaces selectively engaging said table, the wheel grinds a cutting surface on the upwardly facing end of the tool which is inclined at a 60-degree angle to the opposing straight side of the tool.

References Cited in the file of this patent UNITED STATES PATENTS 1,368,472 Barth Feb. 15, 1921 2,317,996 Landy May 4, 1943 2,362,306 Ringzelli Nov. 7, 1944 2,375,358 Hart May 8, 1945 2,385,902 Wilson Oct. 2, 1945 2,595,950 Keebler May 6, 1952 

